Process for making paper and paper made therefrom using liquid cationic starch derivatives

ABSTRACT

NOVEL LIQUID CATIONIC STARCH DERIVATIVES PREPARED BY REACTION OF STARCH WITH EPICHLOROHYDRIN-AMMONIUM HYDROXIDE CONDENSATES ARE USEFUL AS ADDITIVES IN THE MANUFACTURE OF PAPER WHEREIN THEY INCREASE THE RETENTION OF INORGANIC PIGMENTS BY THE CELLULOSE PULP AND STRENGTHEN THE RESULTING PAPER.

United States Patent O US. Cl. 162-175 8 Claims ABSTRACT OF THEDISCLOSURE Novel liquid cationic starch derivatives prepared by reactionof starch with epichlorohydn'n-ammonium hydroxide condensates are usefulas additives in the manufacture of paper wherein they increase theretention of inorganic pigments by the cellulose pulp and strengthen theresulting paper.

RELATED APPLICATIONS This application is a continuation-in-part of ourcopending application Ser. No. 15,199, filed Feb. 27, 1970, now Pat. No.3,666,751, which, in turn, is a continuationin-part of application Ser.No. 811,649, filed Mar. 28, 1969, and now abandoned and assigned to theassignee of the subject application.

BACKGROUND OF THE INVENTION Cationic starch derivatives are useful asadditives in a variety of industrial applications. For example, cationicstarch derivatives are often used in the paper manufacturing industryand in other industries as flocculating agents for colloidal solutions.Moreover, they are particularly useful as beater and/ or headboxadditives in the manufacture of paper wherein their inherent cationiccharge significantly improves the retention of inorganic pigments, aswell as of starch, by the cellulose pulp and thereby substantiallyincrease the strength of the finished paper. US. Pat. 2,813,093, whichissued on Nov. 12, 1957 to C. G. Caldwell and O. B. Wurzburg describesthe preparation of a dry cationic starch by the etherification of starchmolecules with a substituent radical containing a tertiary amino group.With dry cationic starches, however, it is ordinarily necessary to addwater and heat or boil the resulting mixture so as to eifect itsdispersion before it can be utilized in most end use applications.Needless to say, there are many advantages in being able to prepare suchcationic starch derivatives in liquid dispersed form. Thus, a distinctadvantage of the dispersed cationic starch products of this invention istheir ready applicability which is attained without requiring theirdispersion as by cooking or mixing with water prior to their use. Otheradvantages includes, for example, the convenience afforded in being ableto measure, by volume, the necessary concentration of cationic starchproduct which is to be used.

It is the prime object of this invention to provide a process forpreparing cationic starch derivatives directly in liquid dispersed form.

It is another object of this invention to provide a cationic starchderivative in liquid dispersed form.

It is still another object to utilize these cationic starch derivativesin the manufacture of paper.

Various other objects and advantages of this invention will becomeapparent from the further disclosure which follows:

Patented June 5, 1973 ice DETAILED DESCRIPTION OF THE INVENTION We havenow found that cationic starch derivatives can be prepared directly inliquid form, i.e. dispersed form, by means of a process whereby starchis reacted, under controlled conditions, with a condensate ofepichlorohydrin and ammonium hydroxide.

It is believed the dispersed cationic starch derivatives of the presentinvention correspond to a formula given by the following:

X is selected from the group consisting of n has a value of from 0 to 5,Z is selected from the group consisting of Y is selected from the groupconsisting of OH, NHZ9 H R N lags} R R i R groups wherein R is selectedfrom the group consisting of alkyl, hydroxyalkyl and carboxyalkyl groupswith the alkyl portion thereof containing from about 1 to 4 carbon atomsand A represents an anion selected from the group consisting ofchloride, bromide, iodide, phosphate, and sulfate anions.

It is to be noted that the actual value of n is difficult to determineprecisely. However, since these are condensation reactions, the probableforms may occur in varying proportions depending on reagent ratios and,to some degree, on reaction conditions.

It is well known that the cationicity of primary, secondary and tertiaryamines is dependent upon the pH of the system. At low pH levels, theseamines tend to be strongly cationic. At high pH levels these amines donot ionize and are, in essence non-ionic. Quaternary amines, on theother hand, are cationic under all pH conditions. By cationic starch ismeant a starch carrying a positive charge which causes attraction ormigration to the cathode. By the term cationic starches as used in thespecification and claims herein, we mean starch products which containany of the amine groups listed herein and mixtures thereof. Suchstarches are characterized by higher cationicity than the base fromwhich the derivative was prepared. The presence of other modifyinggroups, such as anionic groups, on the starch would tend to change thedegree of cationicity of the product, depending on the pH level of thesystem.

Accordingly, the products of our invention may properly be described asliquefied, i.e., dispersed, amine starch derivatives. In more details,now, the process which leads to the preparation of these novelderivatives may proceed as follows.

The starch, which comprises the base material for the reaction with theepichlorohydrin-ammonium hydroxide condensate, can be selected fromamong a number of starch types. Suitable starches include unmodifiedstarch, as well as acid modified, dextrinized, hydrolyzed, oxidized, andderivatized starches such, for example, as starch ethers and starchesters which still retain reactive sites. The ester groups may, however,be hydrolyzed in the alkaline medium depending upon the specificreaction conditions. These starches may be derived from any sourcesincluding corn, wheat, potato, tapioca, waxy maize, sago, or rice, aswell as from the so-called high amylose starches. Similarly applicableare the amylose and amylopectin fractions of starch. The use of the termstarch is thus intended to include any amylaceous substances, whethermodified or unmodified, which still retain free hydroxyl groups.

The epichlorohydrin-ammonium hydroxide condensate which is used to reactwith the starch is prepared by admixing epichlorhydrin with aqueousammonium hydroxide in approximately equimolar proportions whilemaintaining the temperature of the system below about 60 C. andthereupon agitating the mixture for a period of from about 1.5 to 16hours. Water may be used to dilute the reaction mixture if desired. Itis to be understood that the condensation reaction between theepichlorohydrin and ammonium hydroxide should go essentially tocompletion and may, thus, require a longer reaction period at lowertemperatures and a shorter reaction period at higher temperaturesapproaching 60 C It is desirable to obtain an essentially completereaction between the epichlorohydrin and the ammonium hydroxide whileavoiding any appreciable epichlorohydrin-ammonium hydroxide polymerformation. The condensation may be carried out at temperatures of fromabout 10 to 60 C., or higher. Preferably, a temperature of about 15 C.and a reaction period of from about 2 to hours is used.

The proportions of epichlorohydrin and ammonium hydroxide which are usedmay vary within a range of from about 0.8 to 3 moles of epichlorohydrinto 1 mole of ammonium hydroxide. Condensates prepared usingsubstantially more than 3 moles of epichlorohydrin tend to be moredifiicult to prepare and are less satisfactory in the process of thepresent invention since they tend to cross-link the starch to anundesirable degree and may thus require the use of special precautionarymeasures. On the other hand, condensates prepared using less than 0.8mole of epichlorohydrin per mole of ammonium hydroxide lack reactivesites. Optimum results are obtained with the use of about equimolarportions of the two reagents. When the condensation is completed, theresulting reaction product may be used as is, or it may be adjusted byevaporation or dilution to a solids content of at least about by weight.The evaporation is conducted under reduced pressure while maintainingthe temperature at less than about 70 C. As an optional step, the pH ofthe liquid condensate may, if desired, be adjusted to a level of about3.0 prior to its evaporation in order to prevent the occurrence of anyfurther condensation reaction or polymer formation.

In reacting the starch with the epichlorohydrin-ammonium hydroxidecondensate, the starch may be first suspended in water and the resultingsuspension heated at temperatures from about 80 to 160 C. for asufficient period of time to effect gelatinization of the starch. Theconcentration of the aqueous starch suspension may vary from about 1part of starch to about 3 to\50 parts of water. Suspensions comprising 1part of the starch to about 5 to 10 parts of water aremost satisfactory.

After gelatinizing the starch, the mixture is cooled to about 40 C.,although the temperatures may be adjusted to a range of 25 to C.depending upon the gelatinization temperature, and a suflicientconcentration of a base, such as an alkali metal hydroxide, quaternaryammonium hydroxide, tetramethyl guanidine, or the like, is thereuponadded in order to maintain the mixture at a pH greater than 11 duringthe subsequent reaction. In a variation of the above procedure, thealkali may, if desired, be added prior to the gelatinization of thestarch. [With stirring, the epichlorohydrin-ammonium hydroxidecondensate, as prepared by the above described procedure, is then addedto the gelatinized starch and is allowed to react therewith at thetemperature to which the gelatinized starch has been cooled, i.e. fromabout 25 to 100 C. and preferably at a temperature from about 35 to 45C., for a period of about 4 to 18 hours until the reaction isessentially complete. Note that the reaction may also be conducted atelevated pressure utilizing reaction temperatures of from about 100-130C. If necessary, additional water may be added to dilute the reactionmixture. Upon completion of the reaction, the mixture, if desired, maybe acidified to a pH level of from about 5 to 6 using any convenientacid, with hydrochloric or sulfuric acids being preferred for economicreasons. With regard to the proportions of starch andepichlorohydrin-ammonium hydroxide condensate which may be utilized, Weprefer to use about 1 part, by weight, of the condensate solids withabout 1 to 20 parts, by weight, of dry starch. The actual proportionschosen are dependent on the degree of conversion or fluidity of theparticular starch used in the reaction. Thus, to achieve comparableretention performance, higher proportions of theepichlorohydrin-ammonium hydroxide condensate solids with respect to thestarch are required where a thin boiling starch is used. On the otherhand, where higher viscosity starches are used, lower proportions of theepichlorohydrin-ammonium hydroxide condensate solids with respect to thestarch are required.

In a variation of the above described method for making the cationicstarch products of our invention, we have found that they can also beprepared by a continuous process. In accordance with the latter process,a slurry is formed of the uncooked starch, water, reagent (thepreviously described epichlorohydrin-ammonium hydroxide condensate) andsufiicient alkali to bring the pH of the slurry to about 11 throughoutthe course of the reaction. This slurry is then passed through acontinuous cooker. The term continuous cooker refers to a type ofequipment well known in the starch processing field, and comprisesequipment through which a starch slurry is passed on a continuous basisand subjected to heat, usually in the form of injected live steam, sothat the starch is discharged in a completely gelatinized (cooked)state. When used to make the starch derivative of our invention, thecontinuous cooker method results in the essentially simultaneousgelatinization of the starch and its reaction with theepichlorohydrin-ammonium hydroxide condensate, with the liquid dispersedcationic starch product being discharged from the cooker in continuousfashion. One of the major advantages of this continuous method is itsspeed, the reaction taking place in fractions of a minute as contrastedto the hours required by the batch method at lower temperatures. Thecontinuous method is advantageous, where the batch method is conductedat temperatures of from 100130 C., inasmuch as it enables thepractitioner to avoid the cumbersome equipment and operationsnecessarily employed in the batch method. Furthermore, all of theprocesses and particularly the continuous method conveniently enablesthe practitioner to prepare the starch product at the site of itseventual application and thus have a continuous flow of product forimmediate use.

While the proportion of reagent to starch is within the same magnitudeas already described for the batch process, there are other conditionswhich require special care.

Remembering that the degree of gelatinization of starch in a continuouscooker system is affected by a number of variables, including thealkalinity of the slurry, the speed at which the slurry passes throughthe cooker and the temperatures achieved, it is important that thestarch be subjected to sufiicient heat within the cooker so as toachieve gelatinization and reaction of the starch. Ordinarily, thisrequires that the starch slurry within the continuous cooker be heatedto at least 80 C., and preferably at least 120 C., the latter minimumtemperature eifecting a good balance of reaction efficiency and reactiontime. Preferably, the epichlorohydrin-ammonium hydroxide condensateshould be added immediately before the starch mixture is passed throughthe cooker in order to avoid crosslinking of the starch granules.

If desired, the reaction of the starch with the epichlorohydrin-ammoniumhydroxide condensate may be carried out in the presence of across-linking inhibitor which acts to reduce the occurrence ofcross-linking during the reaction. Such inhibitors include, for example,ammonium hydroxide; alkyl amines such as ethylamine, and diethylamine;alkanol amines such as ethanolamine, and triethanolamine; andalpha-chloro carboxylic esters and acids such as sodium chloroacetate.They may be present in a concentration of about 1 to 15%, by weight,based on the weight of the starch. Furthermore, we believe that when thereaction mixture is more extensively diluted with water and/orcross-linking inhibitors are utilized, the resulting reaction tends toproduce a major proportion of mono-starch substituted derivatives, i.e.the products which are represented by Formula II and Formula III whereinboth Xs are hydrogen, as shown in the structural representation,hereinabove. Likewise, the use of a less dilute reaction medium and/orthe complete omission or the use of smaller concentrations ofcrosslinking inhibitor would tend to result in the preparation of amajor proportion of the tri-starch substituted product as illustrated inFormula III hereinabove, wherein each X in the latter formula representsthe C H:- C H- O Hz-O-Starch radical. The remaining possibilities, i.e.the derivatives representated by Formulas I and II and those derivativesrepresented by Formula 111, wherein one of the X groups represents the Hradical and the remaining X group represents the O Hz-C H-C Hr-O-Starchradical, will be produced in a mixture containing a major proportion ofthese latter types of derivatives under reaction conditions falling inbetween the two extremes called for in the previously describedconditions with respect to the dilution and/or the use of cross-linkinginhibitors.

Thus, it can be anticipated that any given reaction of starch with theepichlorohydrin-ammonium hydroxide condensate will produce a mixture ofvarious liquid dispersed cationic starch derivatives coming within thescope of Formulas I, II and III with the precise composition of eachmixture being determined by the character of the epichlorohydrin-ammoniacondensate, the extent of the dilution of the reaction mixture, and/orthe concentration of the cross-linking inhibitor. Detrimentalcross-linking can also be avoided or reduced by great dilution of thereaction mixture with water, or by the use of converted starches.Ordinarily, it would have been expected that a reaction of this typewould result in substantial cross-linking along with undersirable gelformation. It is surprising, therefore, that satisfactory products can,in fact, be obtained with the novel process of this invention.

The liquid dispersion of cationic starch derivative resulting from theabove described process should have a solids content in the range offrom 1 to 25%, by weight, depending largely upon the method ofpreparation and may 'be preserved against microbial deterioration by theaddition of formaldehyde, phenolic bactericides, or other desiredpreservatives.

The novel products of this invention can be utilized as papermakingadditives in order to improve the retention of starch and inorganicpigments by the stock, i.e. by the cellulose pulp, as well as toincrease the strength of the paper. The dispersed starch derivatives ofthis invention may be employed in papers prepared from all types ofcellulosic fibers and combinations of cellulosic and non-cellulosicfibers. The cellulosic fibers which may be used include bleached andunbleached soda, neutral sulfite, semi-chemical, chemi-ground wood andground wood. Applicable non-cellulosic fibers include polyamide,polyester and polyacrylic resin fibers as well as mineral fibers such asasbestos and glass. Furthermore, these starch derivatives may beeifectively used in the presence of a wide variety of paper additivessuch as clay, talc, titanium dioxide, calcium carbonate, alum, sizingagents, dyes, etc. and may be employed in any of the conventionalmethods of preparing paper sheets and other paper products. In practice,the cationic starch is introduced into the beater, hydropulper, stockchest, or headbox, or at any desired combination of the latterlocations, at any point during the normal course of the papermakingprocess prior to the ultimate conversion of the wet pulp into a dry webor sheet, i.e. at any stage prior to passing the stock onto the dryingstage. They may be employed in concentrations of at least about 0.1%, byweight, based on the solids content of the cationic starch product withrespect to the dry weight of the dispersed pulp. On the other hand,there are no particular advantages to utilizing more than about 2.0%, byweight.

The following examples will further illustrate the em bodiment of ourinvention. In these examples, all parts given are by weight unlessotherwise noted.

EXAMPLE I This example illustrates the preparation of several of thenovel liquid cationic starches of the present invention and alsodemonstrates their utility as pigment retention aids in the manufactureof paper.

Part (A).--An epichlorohydrin-ammonium hydroxide condensate was preparedby slowly adding 185 parts (2.0 moles) of epichlorohydrin to 120 parts(2.0 moles) of concentrated ammonium hydroxide (29%) in 1,000 parts ofwater. The temperature was maintained at about 15 C. by the applicationof external cooling throughout the course of the addition. The mixturewas agitated at room temperature for about 16 hours after which time itwas evaporated to about solids while under reduced pressure and whilemaintaining the temperature below 20 C.

Part B(I).Fifty parts of thin boiling cornstarch which had been preparedby reaction of raw cornstarch with sodium hypochlorite solution until ithad been converted to a degree known in the trade as fluidity, weresuspended in 250 parts of water, heated for twenty minutes on a boilingwater bath, and cooled to 40 C. after which time 16.8 parts of a 50%, byWeight, aqueous solution of sodium hydroxide was added. At this point,31.5 parts of the epichlorohydrin-ammonium hydroxide condensate, asprepared in Part A hereinabove, were added with stirring while thetemperature was maintained at 40 C. As the viscosity increased, thereaction mixture was gradually diluted by the addition of small portionsof water. Thus, after 35 minutes, an additional parts of water had beenadded. After 1.5 hours the system was acidified with 20 parts ofconcentrated hydrochloric acid. The final pH of the system was 5.2 andthe resulting liquid cationic starch reaction product had a solidscontent of 13%, by weight.

.Part B(2).Twenty-five parts of thin boiling waxy maize starch which hadbeen prepared by reaction of raw waxy maize starch with aqueous mineralacid until it had been converted to a degree known in the trade as 85fluidity, were suspended in 250 parts of water, heated for 30 minutes ona boiling water bath, and cooled to 40 C., after which time 16.2 partsof a 50%, by weight, aqueous solution of sodium hydroxide was added.With stirring, 15.75 parts of the epichlorohydrin-ammonium hydroxidecondensate, as prepared in Part A hereinabove, were added and thetemperature was maintained at 40 C. for a total period of 18 hours. Thesystem was then acidified with 20 parts of concentrated hydrochloricacid. The resulting liquid dispersed cationic starch reaction producthad a solids content of 12% by Weight.

Part B(3).-TWenty-five parts of thin boiling waxy maize starch which hadbeen prepared by reaction of raw Waxy maize starch with aqueous mineralacid until it had been converted to a degree known in the trade as 85fluidity, were suspended in 250 parts of water and 16.2 parts of a 50%,by Weight, aqueous solution of sodium hydroxide was added with stirring.While stirring was continued, the mixture was heated to 40 C. and maintained at that temperature for about 1 hour. At this point, 1.7 parts ofdiethylamine followed by 15.70 parts of the epichlorohydrin-ammoniumhydroxide condensate, as prepared in Part A hereinabove, were added andthe reaction was continued at 40 C., with stirring, for a total of 16hours. The system was then acidified with 20 parts of concentratedhydrochloric acid. The resulting liquid cationic starch reaction producthad a solids content of 15 by weight.

Part B(4).The procedure of Part B(3) was repeated using 25 parts of thinboiling cornstarch as described hereinabove with the exception, in thisinstance, that the addition of the diethylamine was omitted. Theresulting liquid cationic starch reaction product had a solids contentof 15%, by weight.

In order to determine the eifectiveness of these reaction products aspigment retention aids, each of the above described liquid cationicstarches was added to the headbox during the normal course of aconventional papermaking process. In each case, the reaction product wasadded in a concentration of 0.25%, by weight, based on the solidscontent of the starch product with respect to the dry Weight of thedispersed pulp. The cellulose pulp also contained 10% of titaniumdioxide, based on the dry weight of the pulp. The degree of pigmentretention, i.e. the percent, by weight, of the initially added pigmentthat was present in the resulting paper sheets in which thesederivatives were homogeneously dispersed, was then determined by ashingthe paper and weighing the resulting ash.

The following table presents the data obtained.

TABLE I Starch solids, percent added Percent retention of titaniumdioxide pH 7.6 pH 6.0

Starch product Product oi 1 Acidity adjusted with aluminum sulfate. 3The data for the blank were obtained from a series of determinations.

rowwwm In addition, the strength of the paper containing the liquidcationic starch was substantially increased as compared to the controlsample.

EXAMPLE I-A This example illustrates the preparation of additional novelliquid cationic starches of the present invention utilizing a continuouscooker and also demonstrates their utility as pigment retention aids inthe manufacture of paper.

Part A(1).-The epichlorohydrin-ammonium hydroxide condensate used hereinwas prepared as described in Part A of Example I with the exception thatthe evaporation step was omitted and the reaction was conducted so as toresult in a condensate having about 39% solids.

Part A(2).The epichlorohydrin-ammonium hydroxide condensate was areaction product of 3 moles of epichlorohydrin and 1 mole of ammoniumhydroxide. The preparation involved the slow addition of 287.6 parts Olfepichlorohydrin to 59.5 parts of concentrated (35%) ammonium hydroxidesolution which was dissolved in 350 parts of water while maintaining thetemperature of the reaction mixture at 25-30 C. by external cooling. Themixture was agitated at room temperature for about 18 hours after whichtime it was evaporated to about 86% solids while under reduced pressureand while maintaining the temperature below 40 C.

Part B(1).Seventy-five parts of waxy maize starch were slurried in 3.750parts of water containing 8.5 parts of sodium hydroxide. To this slurrythere was added 19.2 parts of the epichlorohydrin-ammonium hydroxidecondensate, as prepared in Part A(l), hereinabove. Thereafter, theresultant mixture was passed through a continuous cooker at a rate ofabout 1.1 gallons per minute which was adjusted to raise the temperatureof the contents to about C. Lower temperatures in the pressure cookermay be used. These conditions allowed complete dispersion of the starchas Well as its reaction with the epichlorohydrin-arnmonium hydroxidecondensate. The resulting liquid cationic starch product which wasdischarged from the pressure cooker had a solids content of 2.0%, byweight, and a final pH of 11.2.

Part B(2).Seventy-five parts of potato starch were slurried in 3,750parts of water containing 8.5 parts of sodium hydroxide. To this slurrythere was added 38.4 parts of the epichlorohydrin-ammonium hydroxidecondensate, as prepared in Part A(l), hereinabove. Thereafter theresultant mixture was passed through a continuous cooker at a rate of1.4 gallons per minute at a temperature of about 150 C. which allowedcomplete dispersion of the starch as well as its reaction with theepichlorohydrin-ammonium hydroxide condensate. The resulting liquidcationic starch product which was discharged from the cooker had asolids content of 2.8%, by weight, and a final pH of 10.9.

Part B(3).Sixty parts of waxy maize starch were slurried in 1,940 partsof water containing 4.8 parts of sodium hydroxide. To this slurry therewas added 2.8 parts of epichlorohydrin-ammoniumhydroxide condensate(3:1) as prepared in Part A(2), hereinabove. Thereafter, the resultantmixture was passed through a continuous cooker at the rate of about 1.0gallon per minute which was adjusted to raise the temperature of thecontents to about 150 C. These conditions allowed complete dispersion ofthe starch as well as its reaction with the epichlorohydrin-ammoniumhydroxide condensate. The resulting liquid cationic starch product whichwas discharged from the cooker had a solids content of 2.2%, by weight,and a final pH of 10.5.

The effectiveness of these reaction products as pigment retention aidswas determined according to the testing procedure described in ExampleI.

The following table presents the data obtained.

TABLE I-A Starch Percent retention of solids, titanium dioxide percentStarch product added pH 7.6 pH 6.0

Product of- 1 Acidity adjusted with aluminum sulfate.

EXAMPLE II This example illustrates the preparation of a novel liquidcationic starch derivative using potato starch as the base for thereaction.

Ten parts of potato starch were suspended in 300 parts of water and 8parts of a 50%, by weight, aqueous solution of sodium hydroxide wasadded with stirring. While stirring was continued, the mixture washeated to 40 C. and maintained at that temperature for about 1 hour. Atthis point, 5.1 parts of the epichlorohydrinammonium hydroxidecondensate, as prepared in Part A of Example I hereinabove, were addedand the reaction continued for a total of 16 hours. The system wasacidified with 20 parts of concentrated hydrochloric acid. The resultingliquid cationic starch reaction product had a solids content of 6%, byweight.

When tested as a pigment retention aid in the manner described inExample I hereinabove, it was found that this product permitted theretention of 60%, by weight, of titanium dioxide at pH 7.6 and 65%, byweight, of the latter pigment at pH 6.0. Improved retention was alsoobserved at other pH levels.

In another preparation, the above procedure was repeated using 10 partsof potato starch while 1.36 parts of diethylamine were introduced justprior to the addition of the epichlorohydrin-ammonium hydroxidecondensate. The resulting liquid cationic starch product had a solidscontent of 5.6%, by weight.

When tested as a pigment retention aid in the manner described inExample I hereinabove, it was found that this product permitted theretention of 64%, by weight, of titanium dioxide at pH 7.6 and 71%, byweight, of the latter pigment at pH 6.0.

In another preparation 20 parts of potato starch were suspended in 980parts of water and 16 parts of a 50%, by weight, aqueous sodiumhydroxide solution are used. As in the procedure above, the mixture isheated with stirring at 40 C. for one hour. Then parts of theepichlorohydrin-ammonium hydroxide condensate is added and thegelatinized starch reaction mixture placed in a pressure-cooker andheated at roughly 120 C. for 10, 20, or 30 minutes. When tested inpigment retention as described in Example I, the products are effectivein retaining titanium dioxide.

EXAMPLE III This example illustrates the preparation of additionalsamples of the novel liquid cationic starch products of this inventionusing raw waxy maize starch as the starch base.

Fifteen parts of raw waxy maize starch were suspended in 350 parts ofwater and 12 parts of a 50%, by weight, aqueous solution of sodiumhydroxide were added with 10 stirring. While stirring was continued, themixture was heated to 40 C. and maintained at that temperature for 1hour. At this point, 2.4 parts of diethylamine followed by 1.52 parts ofthe epichlorohydrin-ammonium hydroxide condensate, as prepared in Part Aof Example I hereinabove, were added and the reaction continued for atotal of 16 hours. The system Was acidified to pH 5.0. The resultingliquid cationic starch product had a solids content of 6.4%, by weight.

When this product was tested as a pigment retention aid in the mannerdescribed in Example I hereinabove, it was found that it permitted theretention of 65%, by weight, of titanium dioxide with a paper stockwhich was at a pH of 7.6.

Similar pigment retention results were obtained with products which wereprepared with diethylamine inhibitor using 10, 20, 30, 40 and 50%, byweight, respectively, of the epichlorohydrin-ammonium hydroxidecondensate as based on the amount of dry starch. Comparable treatmentsbased on raw waxy maize starch were prepared without diethylamine beingpresent in the reaction system and were found to yield highlycross-linked products.

EXAMPLE IV This example illustrates the attempted preparation of thenovel liquid cationic starch products of this invention by means of abatch operation using temperatures and reaction periods outside of thespecified ranges re quired for each of the latter variables.

Part A.An epichlorohydrin-ammonium hydroxide condensate was prepared byslowly adding 92.5 parts (1.0 mole) of epichlorohydrin to 60 parts (1.0mole) of concentrated ammonium hydroxide (29%) in 500 parts of water.The temperature was maintained at about 15 C. by the application ofexternal cooling through out the course of the addition. The mixture wasagitated at room temperature for about 16 hours, acidified to about pH3.0 with dilute hydrochloric acid and evaporated to dryness while underreduced pressure and while maintaining the temperature below 20 C.

Part B.Forty parts of thin boiling waxy maize starch which had beenprepared by reaction of raw waxy maize starch with aqueous mineral aciduntil it had been converted to a degree known in the trade as fluidity,were suspended in parts of water and heated for 30 minutes on a boilingwater bath after which time 16.8 parts of a 50%, by weight, aqueoussodium hydroxide solution were added and the mixture cooled to roomtemperature. At this point, 45 parts of the epichlorohydrin-ammoniumhydroxide condensate whose preparation was described in Part A of theexample, were added with stirring, and samples of the reaction mixturewere taken after a period of 0.5, -1.0, 2.0, and 20 hours, respectively.The reaction was terminated, in each instance, by the addition ofconcentrated hydrochloric acid in order to adjust the pH of the reactionproduct to a level of 4.0.

When tested as pigment retention aids in the manner described in ExampleI hereinabove, it was found that the first three products permitted theretention, at pH 7.6, of 52% or less, :by weight, of titanium dioxide.The product obtained by the use of a 20 hour reaction period was in theform of a gel, indicative of excessive crosslinking, and could nottherefore be tested.

EXAMPLE V This example illustrates the preparation of two of the novelliquid cationic starch derivatives of this invention using potato starchas the base and wherein the epichlorohydrin-ammonium hydroxidecondensates were prepared using other than equimolar proportions of thetwo reagents comprising the condensate.

Ten parts of potato starch were suspended in 300 parts of water and 8parts of a 50%, by weight, aqueous solution of sodium hydroxide werethen added with stirring. While stirring was continued, the mixture was

